The present invention relates to machines for the metered pouring of fluid or "flowing" products (for example, liquid, creamy or pasty products).
1. Field of the Invention
Machines of this type (currently known as "pouring" and/or "batching" machines) are used widely in various sectors of industry and particularly in the food industry for pouring measured quantities of liquid, creamy or pasty products such as, for example, fillings, stuffings or trimmings for food products such as confectionery.
Most pouring/batching machines of the prior art provide for the use of metering and delivery cylinders. Pistons which are movable substantially sealingly in the cylinders can perform a first sliding stroke within their respective cylinders, during which each piston draws in or admits a certain quantity of the product to the cylinder, and a delivery stroke, which is usually performed in the opposite direction from the loading stroke, and during which the piston expels from the cylinder, usually through a nozzle at its end, a measured quantity of the material previously loaded into the cylinder.
A solution of this type is described, for example, in U.S. Pat. No. 4 787 534.
Another type of batching machine which is very widespread uses a manifold. In this case, the product to be poured is sent towards a manifold in a substantially continuous flow (that is, under dynamic conditions), several supply ducts or nozzles branching out from the manifold and usually being controlled by valve or tap structures, which can be moved alternately to open and closed positions, so as to discharge measured quantities of the product from the manifold.
Both the solutions described above have been found unsatisfactory in practice when the product to be delivered is an aerated product, that is, a product which contains a certain amount of gaseous or aeriform substances trapped within it. This is the case, for example, with the so-called meringue mixture which is used in the food industry (particularly in the confectionery industry) and which is prepared by whipping egg whites and sugars to a froth, usually with the addition of flavourings. A mass of meringue mixture has a specific gravity of the order of 0.5-0.6 combined with an intrinsic resilient mechanical compressibility due to the presence of the air trapped within the mixture.
Other aerated products currently used in the food industry are, for example, whipped cream, mayonnaise, sponge-cake mixture, etc.
The pouring of aerated products by machines with pistons of the type described above has the disadvantage that, precisely because of the large quantity of air in the product, conditions may arise in which the machine has great difficulty both in loading the product (for example, it may load a smaller quantity than envisaged as a result of the drawing-in of a large quantity of air) and in delivering the product (which tends to take place in spurts so that the product delivered is unevenly distributed).
In the case of machines with manifolds, in addition to these problems, it is also difficult to ensure that the product delivered is distributed evenly by the various metering nozzles; this is due--primarily--to the different paths which the flow of the product has to follow to reach the nozzles.
These problems mean, amongst other things, that there is a marked difficulty in precisely metering the quantity of the product delivered during each pouring operation.
Although this difficulty is tolerable when the quantity of the product delivered during each pouring operation is quite large, in practice, it is insurmountable when very small measured quantities (for example, of the order of 1/2 cm.sup.3) of an aerated product with a low specific gravity (0.5-0.6--as in the case of meringue mixture or even lower values, for example 0.3) are to be delivered.